Polymorphism of Amorphous Ge2Sb2Te5 Probed by EXAFS and Raman Spectroscopy

The local order of amorphous Ge2Sb2Te5 films (50 nm) prepared by sputtering (AD), melt quenching (MQ), or ion irradiation (II) has been probed by EXAFS and Raman spectroscopy. The Ge K edge of the AD sample shows a stronger contribution from homopolar Ge-Ge bonds with respect to irradiated films. Raman spectroscopy measurements indicate a greater abundance of homopolar Te-Te bonds in AD film with respect to MQ and II. Irradiation of deposited amorphous GST films results in a reduction of "wrong" homopolar bonds. This variation is probably the origin of the faster crystallization speed of MQ and II amorphous samples. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.019112esl] All rights reserved.